Six years ago, Miranda Petrone was a soon-to-be 13-year-old having a fun President's Day walk on the beach with her dad. Moments later, she was staking a claim in Oregon history as she stumbled upon what turned out to be one of two cannons found that day believed to be from the USS Shark.

"We were going on a walk ... and my dad said, 'Look Miranda, it's a cool rock.' I was like 'Yeah, sure.' I walked over. It was basically just a big black rock looking thing. It wasn't noticeably a cannon and then I saw rust on it and rocks don't rust and that made us interested a little bit more. I was always like 'I am going to find treasure on the beach,' and then one day I did."

Now, for the first time since Petrone's discovery, the public will have a chance to see those cannons as the Columbia River Maritime Museum in Astoria unveils its newest exhibit. Opening May 24, the exhibit features the cannons, an officer's sword from the ship found in the 1970s and Shark rock, a large boulder into which survivors of the shipwreck carved their name.

"We're honored," said Dave Pearson, deputy director of the museum. "We're very excited about it. We are a maritime museum, but it is so much more than that. This is Oregon's story. This is at the dawn of the Oregon territory. These artifacts never before displayed are a key component of Astoria 168 years later."

Admission: $12 adults; $10 seniors 65 and older; $5 children 6-17, no charge for children 6 and under

Hours: Seven days a week, 9:30 a.m. to 5 p.m.

The USS Shark wrecked at the mouth of the Columbia River in 1846. The crew survived, but much of the wreckage sank. Some, however, washed ashore 70 miles south of Arch Cape.

In 1898, one of the cannons – technically a carronade, the term for a shorter style cannon – was recovered from an Arch Cape beach. It's been on display at the Cannon Beach History Center, but was recently shipped to Texas A&M University for conservation.

When Petrone found the cannon, it was almost completely encased in rock welded together with hardened sand in a shell called a concretion, said Chris Havel, spokesman for the Oregon Department of Parks & Recreation.

"The guns were still sitting on the big wooden sleds used to attach them to the deck, and some of the wood was exposed. While park staff were investigating the find, another visitor found what appeared to be a second encrusted cannon closer to the ocean."

The two cannons were shipped to Texas A&M, where students in the Nautical Archeological Program carefully worked with hand and precision power tools to remove the more than 100 years of concretion.

Once the hardened sand and rock were removed, the cannons were sent to a electronic reduction vat for nine months to pull out the chlorides that leached into the metal from the salt. That was followed by a good boiling to remove the chemicals used to clean it up.

And now, the cannons are back in Oregon. While still the property of the U.S. Navy, the guns are at the museum under a loan agreement with the federal government. The state worked closely with the Navy to find the best site to display the old weapons.

"The normal place to take artifacts like these that are found on state ground is to the Museum of Natural and Cultural History at the University of Oregon," Havel said. "But first, on the practical side, these are pretty big. We had to choose where should they be to tell the story in the right way? You want it to be as close to the place they were found. The Shark went down at the mouth of the Columbia. Where closest to the mouth is a place that has museum professionals that can take care of an object like this, can curate responsibly and are capable of sharing the story of the carronades on the Shark?

"If you pose that question there is really only one answer. The Columbia River Maritime Museum is a world-class facility with curation professionals and education professionals."

Along with those getting a first glimpse of the refurbished cannons will be Petrone and restorer Brennan Bajdek, who was a first-year student at Texas A&M when the guns arrived. He worked on the cannons for several years before finishing his nautical archeological studies.

"This will be the first time I'll see the entire collection together," said Bajdek, who has since moved to Portland where he is a supervising archeologist with Archeological Investigation Northwest. "I wasn't at A& M when the wooden carriages came out. They were still in treatment. It will be nice to see everything put together see how it all looks. I feel proud. I feel like the work we did really reflects in the end project."

Likewise, Petrone, who was featured in a PBS documentary on the cannons, is excited to see the exhibit. "My dad told me about the opening. I said, 'You're joking.' I just can't even believe it. I am really looking forward to it."